Users of portable devices generally prefer small and light devices to larger, heavier alternatives. Portable medical devices such as controllers of mechanical circulatory systems (MCS) are carried on a person at all times and thus benefit greatly from a small portable design. One type of MCS is a ventricular assist device (VAD). A challenge for manufacturers is to reduce the size and weight of devices while still providing the reliability and ease of usability that users expect.
VADs are implanted in a patient and controlled by a system controller through a percutaneous connection. The VAD comprises a heart pump to provide assisted blood flow for a patient. A percutaneous (drive line) connection couples the system controller, comprising a motor controller and one or more batteries, to the implanted heart pump. Ventricular assist systems with their coupled system controller must provide for uninterrupted blood flow assistance for the patient (user) and therefore benefit from a design that is portable as well as robust.
VADs have typically been implanted for use in late stage heart failure (Class IV) patients. Some VAD systems allow patients to carry a portable system controller and batteries to allow for untethered operation of their heart pump. Typically, these patients can attain a high degree of mobility and freedom, as demonstrated by quality of life measures, however the peripheral devices (including the system controller and batteries) the patients must carry and manage remain cumbersome. Adoption of VAD systems is expected to expand to include less-sick (i.e. Class III) heart failure patients. Patient quality of life will be a significant factor in determining VAD acceptance with Class III patients. Therefore, more robust and intelligent device connections are needed to provide decreased risk of infection, decreased risk of power faults, and greater ease of use for patients.
Current VAD systems are easily identifiable as a medical device and can require two or more large batteries worn on the patient. Often each battery is coupled to the system controller by a long cable connection to allow for even weight distribution of each battery located externally from the system controller. More cables, connections, and weight create a greater likelihood of trauma to the exit site during routine movements of the patient. It is preferable for patients to have a device small enough to conceal beneath clothing. Also, from a quality of life perspective, patient worn peripherals should be as unobtrusive to the patient as possible. VAD cables can tangle and cause undue stress to an exit site where the percutaneous connection leaves the body. Stress at the exit site leads to skin breakdown or trauma and put the patient at risk of infection. Furthermore, the current cables and electrical connections result in components that are susceptible to water, dust or other elements. Devices having multiple exposed electrical connections also contain a higher risk of shorting out the medical device through unintended connections. Patients using current systems must take special care when maintaining and using their devices.
Current medical devices also do not allow for multiple input and output options for their medical devices. Patients must choose systems with advanced touch screen interfaces that are relatively large, or choose smaller but potentially less flexible displays with separate buttons or switches. Therefore, greater flexibility for VAD systems is needed in order to allow their device to be as portable as possible in certain situations, without sacrificing usability.